Great story and it just might be that Sinatra and Jack E. Leonard coordinated this and had a running joke doing this. Your friend may not have been the only one this was done to. In wikipedia it has Jack E. Leonard complaining at a roast that “Don Rickles has been doing my act for twelve years”
I never thought of that but it’s possible. But I will say, he was obnoxious at that table that one day. Loud, rude, even belligerent. Sure, I was the only other person in the whole room other than those at the table with him, but that’s no excuse.